A receiver, for example a global positioning system (GPS) receiver, includes an analog-to-digital converter (ADC) that converts an input analog signal to digital samples. Efficiency of the ADC is a function of dynamic range of operation of the ADC. The dynamic range of operation of the ADC in turn is a function of a required Signal-to-Quantum-Noise Ratio (SQNR). Often, the receiver is prone to radio frequency (RF) interference. The RF interference can be of higher magnitude than that of the input analog signal. The higher the magnitude of the RF interference, the higher must be the required SQNR of the receiver and the ADC. However, having high SQNR may not be feasible. Hence, the dynamic range of operation of the receiver and the ADC needs to be utilized optimally to relax the requirement of high SQNR.
In existing receivers, the ADC is coupled to a root-mean-square (RMS) based automatic gain control (AGC) circuit. The RMS based AGC circuit maintains a constant RMS voltage at an input of the ADC. In receivers having the RMS based AGC circuit, the dynamic range of the ADC is efficiently utilized when the input analog signal includes only desired signal. However, in presence of the RF interference, the dynamic range of the ADC may not be utilized efficiently. Further, if the magnitude of the input analog signal is greater than the desired signal, the RMS based AGC circuit may reduce the gain of the receiver to keep combined RMS amplitude of the input analog signal and the RF interference at a constant value.